1. Field of the Invention
The present invention relates to a thermal transfer recording apparatus and its recording method, particularly, relates to a recording method of thermal transfer recording apparatus, which transfers ink having meltability or sublimeness to a recording medium and forms an ink image on a recording medium being extended between a supply reel and a take-up reel.
2. Description of the Related Art
There existed a re-transferring method such that an ink image is once formed on an intermediate recording medium, and then the ink image is transferred to a recording medium. A card recording apparatus utilizing such the re-transferring method has been well known and various ideas have been proposed. FIG. 7 shows a constitution of such a card recording apparatus.
In FIG. 7, the card recording apparatus is composed of an ink film 253 of which a base film in a tape shape is coated with meltable ink or sublimation ink being extended between a first supply reel 251 and a first take-up reel 252, an intermediate recording medium 256 being extended between a second supply reel 254 and a second take-up reel 255, a heating section 257 for transferring ink on the ink film 253 to the intermediate recording medium 256, a platen roller 259 for holding the ink film 253 and the intermediate recording medium 256 in conjunction with a thermal head 258 constituting the heating section 257, and another heating section 263, which is composed of a heat roller 261 and another platen roller 262, for transferring an ink image being transferred to the intermediate recording medium 256 to a recording medium 260.
The ink film 253 and the intermediate recording medium 256 being directly contacted with each other is transported to the heating section 257, wherein ink on the ink film 253 is heated by the thermal head and an ink image is formed on the intermediate recording medium. The intermediate recording medium 256 formed with the ink image is transported to the other heating section 263, wherein the ink image formed on the intermediate recording medium 256 is transferred to the recording medium 260.
The first supply and take-up reels 251 and 252 utilized for transporting the ink film 253 and the second take-up reel 255 utilized for transporting the intermediate recording medium 256 is driven by a DC (direct current) motor. The second supply reel 254 for transporting the intermediate recording medium 256 is driven by a stepping motor.
A stepping motor is a motor of which rotation is controlled by a number of pulses inputted. By using such a stepping motor to drive the second supply reel 254 for the intermediate recording medium 256, an amount of transportation of the intermediate recording medium 256 can be accurately controlled.
Nevertheless, in a case that the second take-up reel 255 for transporting the intermediate recording medium 256 is driven by a DC motor, a rotation speed of the DC motor becomes unstable when the DC motor starts to rotate. Therefore, there existed a problem such that an ink image transferred to the intermediate recording medium 256 is suffering from irregularity in depth. In other words, a DC motor is unstable in rotation, so that an ink image is easily suffering from a problem of irregularity in depth when the DC motor starts to rotate even though the second supply reel 254 is accurately controlled to drive.
FIG. 8 shows a rotation speed of a DC motor when the DC motor is activated to start. As shown in FIG. 8, a rotation speed is not stable for some period of time after the DC motor started to rotate. More accurately, delay in speed occurs at a beginning of rotation and a rotation speed once increases more than a regular transfer speed so as to recover a delayed start timing for transferring, and then the rotation speed approaches the regular transfer speed.
In a case that an ink image is formed on the intermediate recording medium 256 by driving the second take-up reel 255 for the intermediate recording medium 256 in accordance with the above-mentioned characteristic of rotation speed, some load resistance generates at the heating section 257 because the platen roller 259 is pressed against the thermal head 258. Accordingly, the take-up roller 255 can hardly take up the intermediate recording medium 256 so much as to be lead out by the second supply reel 254. In addition thereto, when an ink image is transferred to the intermediate recording medium 256 in the heating section 257, the heat roller 261 is separated from the other platen roller 262, so that no load resistance generates in the other heating section 263.
Therefore, slackening the intermediate recording medium 256 at the heating section 257 in the supply reel 251 side causes irregularity in depth of an ink image transferred to the intermediate recording medium 256. It is possible to prevent the intermediate recording medium 256 from slackening if a rotation force of a DC motor driving the take-up roller 255 is increased so as to increase a tension applied to the intermediate recording medium 256. However, generally, a substrate sheet of the intermediate recording medium 256 is extremely thin as thin as less than 25 xcexcm. Accordingly, there existed another problem such that the intermediate recording medium can not be transported stably due to stretch of the substrate sheet if a tension applied to the intermediate recording medium 256 is increased.
Accordingly, in consideration of the above-mentioned problems of the prior art, an object of the present invention is to provide a thermal transfer recording apparatus and its recording method, which can transfer an ink image without irregularity in depth.
According to an aspect of the present invention, there provided a thermal transfer recording apparatus comprising: an ink film coated with ink having meltability or sublimeness on a tape shaped base film; a supply reel driven by a stepping motor and wound with unused part of a recording medium in a tape shape; a take-up reel driven by a DC (direct current) motor winding used part of the recording medium; and a transferring section for transferring ink on the ink film to the recording medium by heating the ink film and unused part of the recording medium being contacted with each other, wherein the recording medium is recorded with being rewound by the supply reel while transferring ink in the transferring section.
According to another aspect of the present invention, there provided a recording method of a thermal transfer recording apparatus, which comprises an ink film coated with ink having meltability or sublimeness on a tape shaped base film, a supply reel driven by a stepping motor and wound with unused part of a recording medium in a tape shape, a take-up reel driven by a DC motor winding used part of the recording medium, and a transferring section for transferring ink on the ink film to the recording medium by heating the ink film and unused part of the recording medium being contacted with each other, the recording method comprising steps of: forwarding the ink film from a first supply reel to a second take-up reel and the intermediate recording medium from a second supply reel to a second take-up reel; indexing ink on the ink film and a frame of the intermediate recording medium; adjusting the frame to a head of the ink; rewinding the ink film and the intermediate recording medium by the first and second supply reels respectively; and transferring the ink to the frame in the transferring section by heating the ink film and the intermediate recording medium being contacted with each other while rewinding the ink film and the intermediate recording medium by the first and second supply reels respectively, wherein the steps of forwarding, indexing, adjusting rewinding and transferring are repeated as many times as a number of ink to be transferred.
Other object and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.